1. Field of the Invention
The present invention relates to a color electrophotographic image forming apparatus that utilizes a rotatable rotary support member to support a plurality of developing devices.
2. Description of the Related Art
Conventionally, a color electrophotographic image forming apparatus using a rotatable rotary support member (rotary) supporting a plurality of developing devices has been known in the art. Rotating the rotary support member in the color electrophotographic image forming apparatus sequentially moves a plurality of developing devices supported by the rotary support member to a developing position that is opposed to an photosensitive drum. The color electrophotographic image forming apparatus includes a sensor flag that is positioned relative to the rotary support member to detect a self-phase of the rotary support member.
Recent efforts have been towards downsizing a main body of the color electrophotographic image forming apparatus from that in the conventional art. A size of the rotary support member has been decreased in accordance with that downsizing. As a result, the position of the sensor flag has changed to be closer to the center of rotation of the rotary support member compared to the conventional art. This change results in an increase in error. In short, if the main body is downsized, then the detected error of the phase of the rotary support member by the sensor tends to be bigger compared to the conventional art.
For example, if the position of the sensor flag provided on the rotary support member is 50 mm from the center of rotation of the rotary support member, a variation error of a detective precision of the sensor flag is twice as much, compared with the case of 100 mm. This will influence the precision to stop the developing device at the developing position to develop a latent image on the photosensitive drum. Thus, in accordance with the downsizing of the main body of the device, to stop the developing device at the developing position with accuracy compared with a conventional mechanism may be an issue.